Ingeborg and Erwin Hochmair of Med-El, the inventors of the cochlear implant
Photograph: Heinz Troll/theguardian.com

After living most of his life with severe hearing problems, John Cradden grabbed the chance to be fitted with a cochlear implant, or "bionic ear". But throwing away his hearing aids initially made things worse.

"It was frankly disappointing at first. All I heard on my 'switch-on' was just a loud mush – a sound with no discernible sharpness or tone to it," he says.

"But the implant team said it would take time because, essentially, my brain was relearning to hear, through what was an entirely new hearing physiology."

Cradden, 42, was born partially deaf. Up to the age of seven, his condition worsened until he was profoundly deaf. It was after a further deterioration in his mid-30s that he decided to get a cochlear implant.

The elaborate electrical devices are fitted under the skin behind the ear during surgery and help provide sound signals to the brain, giving profoundly deaf people who cannot benefit from hearing aids the ability to hear – in effect, replacing the function of a sensory organ. About 400,000 devices have now been fitted around the world.

"I wear it all the time," Cradden says. "It's easy to live with and I wouldn't be without it. I can use the phone more comfortably than I ever did before. I can still enjoy music. I could go on, but the bottom line is that my speech comprehension is better than it ever was with hearing aids.

"Getting the implant came shortly after the birth of my second child and it was great timing, because to be able to swim along today with the inevitably noisy banter of life with two young children is just priceless."

For Ingeborg Hochmair, seeing a patient benefit from technology for which she and her husband, Erwin, can claim credit is a rewarding experience. In the 1970s, the Hochmairs – known on the campus of the Vienna University of Technology as the "Electronic Couple" – helped create the first microelectronic multi-channel cochlear implant.

The development of the implant allowed users for the first time to understand speech rather than hearing only muffled sound. Med-El, the company co-founded by the Hochmairs in 1980, is now the second-largest producer of cochlear implants in the world, making one-third of all devices fitted each year.

Speaking in the midst of a busy conference hall in Berlin recently, Ingeborg Hochmair said Med-El was constantly striving to improve its technology.

"People can enjoy music – they can converse in surroundings like here, in a foreign language, in a noisy place. If they get implants in both ears, they can localise sounds and have a three-dimensional impression of sound around them. They can feel a real part of the community – it is all about communication nowadays," she said.

Ingeborg Hochmair is now chief executive at Med-El while her husband is a professor of applied physics and microengineering at the University of Innsbruck. In 2013, she was a co-recipient of the prestigious Lasker prize for clinical medical research.

In Britain, around 10,000 people have been fitted with cochlear implants, according to data from the NHS.

"There is even a greater number of people who are only deaf in one ear who now receive an implant in one ear," Hochmair said. "For little children, that is quite important. If you are deaf in one ear, you typically lose a year at school because it takes you half the sentence to understand where somebody starts talking before you can understand everything, so you really have to concentrate hard."

While health systems in the EU allow children to receive a cochlear implant early on in their development, this is not the case in parts of Latin America and south-east Asia.

"In many countries, they just don't hear about it and then you have to get the trust of the people," Hochmair added. "It works as soon as there is a critical number of users, then others will hear about it and also trust the possibilities. In the highly developed [health] systems, the growth is now with adult patients. As people get older, many will develop a hearing loss and it is also known that sometimes cognitive decline follows hearing loss. So people shouldn't wait once they are diagnosed with hearing loss – they should get a hearing aid, and if that is not enough, they should get an implant."

In Britain, the process of implanting and subsequent surgery costs between £38,000 and £45,000. Usually an adult is able to have only one implant on the NHS while children have two. The high price works out in longer-term benefits, argues Hochmair.

"The therapy is cost-effective because it is a life-changing device. If you implant a little child, then it can most likely attend a normal school, it can get a really good education, it can get a good job, it can become a good taxpayer. Even not considering the improvement in the quality of life for the individual, it really works for society."

For Cradden, who is writing a book about his experiences with the working title "The Man Who Misheard His Knife for a Cat", there is a frustration that the technology is sometimes perceived as enabling deaf people to hear instantly whereas many need at least a year after being fitted with a cochlear implant to get the full benefit.

"They may well 'hear' something instantly when they are switched on for the first time, but they won't understand it. Their brains need time to adapt to – and then fully comprehend – the sounds they hear through the implant," he says.

The so-called bionic ear, credited as being the first device to have replaced a sensory organ, stands as a milestone in innovation in medical technology. In Britain, Christofer Toumazou, chief scientist at Imperial College London's Institute of Biomedical Engineering – whose most recent invention was a USB stick that decodes a patient's DNA – was also involved in developing cochlear implants.

In the future, it is hoped that other technological innovations, such as the remote monitoring of patients' blood pressure, weight and oxygen levels, will similarly take pressure off accident and emergency departments and save money for the broader health system.

How does a cochlear implant work?

A cochlear implant consists of an external sound processor that takes in sound and processes it via a minicomputer. The sounds are converted into digital information that is sent internally into the cochlea, the inner part of the ear which processes sound. The signal is then sent along the hearing nerve to the brain as usual. Following the Hochmair's work in the 1970s, people could understand speech rather than only muffled sound.